Device for maintaining operative relation between a dressing tool and grinding wheel



May 9, 1967 H. RUTH 3,318,052

D. DEVICE FOR MAINTAINING OPERATIVE RELATION BETWEEN A DRESSING TOOL AND GRINDING WHEEL Filed Oct. 1, 1964 2 Sheets-Sheet 1 g I f TIHEH INVENTOR DAN/EL H. RUTH W ATTORNEY AIR May 9. 1967 D. H. RUTH DEVICE FOR MAINTAINING OPERATIVE RELATION BETWEEN A DRESSING TOOL AND GRINDING WHEEL Filed Oct. 1, 1964 2 Sheets-Sheet 2 INVENTOR DAN/EL H. RUTH Ian/4&2 TTORNEY EXH.

United States Patent 3,318,052 DEVICE FOR MAINTAINING OPERATIVE RE- LATION BETWEEN A DRESSING TOOL AND GRINDING WHEEL Daniel H. Ruth, Waynesboro, Pa., assignor to Landis Tool Company, Waynesboro, Pa. Filed Oct. 1, 1964, Ser. No. 400,851 6 Claims. (Cl. 51-165) This invention relates to high precision grinding machines, particularly machines which include provision for automatic compensation for dressing.

For many years, it has been the practice in automatic compensation for dressing to advance the grinding wheel and dressing tool by equal amounts so that after a dressing operation, the face of the grinding wheel would be in the same position of advance even though its diameter has been reduced as a result of the dressing operation. This practice does not take into consideration the fact that between dressing operations on a grinding wheel, the diameter of the wheel is reduced by wear. When it comes time to perform a dressing operation, the dressing tool which was in contact with the grinding wheel during the previous dressing operation, is now spaced radially from the grinding wheel face by the amount of wheel wear. In the past, this has been mistaken for dressing tool wear. In both cases, the diamond must be adjusted by the amount of space.

According to established dressing practice, at the beginning of the dressing operation, the dressing tool is advanced a predetermined amount and the grinding wheel is automatically advanced by the same amount. However, because of wheel wear, the advance of the dressing tool does not place the dressing tool in position to reduce the size of the grinding wheel by the amount that the grinding wheel has been advanced. In machines with automatic compensation for dressing and in which size is determined by advancing the grinding wheel support to a positive stop, the grinding wheel will advance to a point beyond the specified size and the work will be ground undersize. This condition must be corrected by manually retracting the grinding wheel face so that it will grind within the prescribed limits.

Where work size is controlled by a gauge which automatically retracts the grinding wheel when size is achieved, and final feed is by a feed screw, compensation for wheel wear is inherent in the grinding feed and is, therefore, not a factor in size control. However, because of the gap between the dressing tool and the grinding wheel due to wheel wear, the dressing tool may have to make one or more idle passes with a feed increment for each pass before it advances far enough to engage the grinding wheel, thus increasing the time required for a dressing operation and advancing the wheel by an amount greater than the reduction in size by dressing. Furthermore, failure to compensate for wheel wear affects wheel approach control in a manner similar to its. effect on size control by a positive stop. Approach control is effected by reducing the feed rate just before the wheel engages the work. Failure to compensate for wheel wear results in the wheel advancing too far before the feed rate is reduced so that it engages the work at a feed rate too fast for grinding with resultant damage to both the wheel and work.

It is, therefore, an object of the present invention to advance the dressing tool periodically between dressing 3,318,052 Patented May 9, 1967 operations by an amount corresponding to wheel wear for a given number of grinding cycles.

Another object is to provide means operable with the feed mechanism to advance the dressing tool after a predetermined number of advances of the feed mechanism.

FIG. 1 is a partial sectional end elevation of a ratchettype feed mechanism.

FIG. 2 is a partial rear view of the ratchet mechanism.

FIG. 3 is a diagram of a pressure system which may be either hydraulic or pneumatic.

Wheel support 10 has means for advancing and retracting grinding wheel 11 toward and from a workpiece W which is similar to that disclosed in US. application Serial No. 260,248, filed Feb. 21, 1963, now US. Patent No. 3,183,631, granted May 18, 1965. Briefly, this consists of a feed screw 20 rotatably mounted in a machine base 21. Feed screw 20 may be rotated in engagement with a thread engaging member in the form of a worm Wheel or pinion 30 at one end of shaft 31 rotatably supported in wheel support 10. Shaft 31 may be rotated manually by hand wheel 35 to advance wheel support 10 relative to feed screw 20 while said feed. screw remains stationary. Wheel support 10 may also be advanced by rotation of feed screw 20 while shaft 31 and pinion 30 remain angularly stationary.

The means for rotating feed screw 20 consists of a worm wheel 40 slidably keyed to a portion of said feed screw. Worm gear 41 may be rotated directly or through a suitable gear train by ratchet 42. Ratchet 42 may be actuated in a clockwise direction by pawl 43 and in a counter-clockwise direction by pawl 44. Both of said pawls 43 and 44 are mounted on pawl carrier 45. Pawl carrier 45 and pawl 43 are actuated in a clockwise direction by means of piston 50 in cylinder 51 to advance wheel support It) for a grinding operation. Fluid under pressure is supplied alternately to opposite ends of said cylinder by reversing valve 52. Carrier 45 may be operated in a counter-clockwise direction by means of piston 53 in cylinder 54 to reset the feed mechanism a specified amount after each grinding operation. Fluid under pressure is directed to cylinder 54 by valve 55.

The means for dressing grinding wheel 11 is a dressing tool 60 mounted on carriage 61. Carriage 61 may be moved endwise by piston 65 in cylinder 66 to pass dressing tool 64} across the face of grinding wheel 11. Dressing tool 60 is mounted in slide 70 on carriage 61 for movement toward grinding wheel 11. Slide 70 is held in operative position or retracted by cylinder 71 and stationary piston 72. Said movement may be effected by ratchet 75 on feed screw 76. Ratchet 75 is actuated by pawl 77 on piston 78 in cylinder 79. Piston 78 is actuated in one direction by fluid under pressure and in the opposite direction by spring 8% Fluid under pressure is directed to the head end of piston 78 by reversing valve actuated by solenoid 91 through pilot valve 92. One means for energizing solenoid 91 is a circuit (not shown) controlled by limit switch mounted in a suitable position adjacent ratchet 42.

The means for actuating limit switch 100 is a cam having lobes 120 or equivalent actuating means and mounted in axially spaced relation with worm gear 41 and ratchet 42 on shaft 111 in bracket 1.12. Rotation of shaft 111 and cam 110 is resisted by brake 115 held against shaft 111 by spring 16.

The means for rotating cam 110 consists of a pin A in ratchet 42 and pin B in earn 110 in the path of rotation of pin A. When ratchet 42 is rotated to advance grinding wheel 11, pin A engages pin B during the final portion of the feeding movement. Because of wheel wear, ratchet 42 must turn a little farther for each successive grinding operation in order to grind the work to the diameter for which a gauge is set to stop the grinding feed operation. Pin B and cam 110 are advanced a corresponding amount.

At the end of each grinding operation, ratchet 42 is reversed by means of reset pawl 44. However, cam 110 remains in the position to which it has advanced when ratchet 42 is reset. Eventually, one of the lobes 120 on cam 110 actuates limit switch 100 to energize dresser feed solenoid 91, shifting pilot valve 92 to the right and reversing valve 90 also to the right. Reversing valve 90 directs fluid under pressure to the head end of dresser piston 78, turning ratchet 75 and feed screw 76 to advance dressing tool 60 in the direction of grinding wheel 11 so that when a dressing operation is initiated, dressing tool 60 will be in position to engage grinding wheel 11 with the proper depth of cut on the first pass.

I claim:

1. In a grinding machine,

(a) a grinding wheel support,

(b) a grinding wheel rotatably mounted on said wheel support,

(c) means for effecting relative feeding and retracting movements of said wheel support including (d) a reversible increment feeding means for said grinding wheel,

(e) said increment feeding means serving to advance said wheel suport progressively farther for each grinding operation because of wheel wear,

(f) said increment feeding means being operable by a fixed amount for retracting said wheel support,

(g) a dressing tool periodically and progressively separated from said grinding wheel because of said wheel wear,

(h) a second increment feeding mechanism for feeding said dressing tool toward the operative face of said grinding wheel,

(i) and means movable with said first increment feeding means and operable after a predetermined number of grinding cycles to actuate said second increment feeding mechanism to advance said dressing tool to operative relation with said grinding wheel.

2. In a grinding machine,

(a) a grinding wheel support,

(b) a grinding wheel rotatably mounted on said wheel support,

(c) means for effecting relative feeding and retracting movements of said wheel support including (d) a reversible increment feeding means for said grinding wheel,

(e) said increment feeding means serving to advance said wheel support progressively farther for each grinding operation because of wheel wear,

(f) said increment feeding means being operable by a fixed amount for retracting said wheel support,

(8) a dressing tool separated from said grinding wheel because of said wheel wear,

(h) a second increment feeding mechanism for feeding said dressing tool toward the operative face of said grinding wheel,

(i) and means actuated progressively by said increment feeding means and operable periodically to actuate said second increment feeding mechanism to advance said dressing tool toward said grinding wheel an amount corresponding to said wheel wear.

3. In a grinding machine,

(a) a grinding wheel support,

(b) a grinding Wheel rotatably mounted on said wheel support,

(c) means for effecting relative feeding and retracting movements of said wheel support including (d) a reversible feeding means for said wheel support,

(e) said feeding means serving to advance said wheel support progressively farther for each grinding operation because of wheel wear,

(f) said feeding means being operable for retracting said wheel support a fixed amount after each grinding cycle,

(g) a dressing tool,

(h) a second feeding means for feeding said dressing tool toward the operative face of said grinding wheel,

(i) said dressing tool and said grinding wheel being periodically spaced apart because of said wheel wear,

(j) and means movable with said first feeding means and operable after a number of grinding cycles to actuate said second feeding means to return said dressing tool to operative relation with said grinding wheel.

4. In a grinding machine,

(a) an increment feeding mechanism having (b) means for retracting a grinding wheel an amount equal to or less than the amount of advance of said grinding wheel for a grinding operation, whereby to compensate for wear of said grinding wheel,

(c) means to dress said grinding wheel comprising (d) a dressing tool,

(e) another increment feeding mechanism for said dressing tool,

(f) and means operable by said first increment feeding mechanism to actuate periodically said other increment feeding mechanism to advance said dressing tool toward said grinding wheel by an amount corresponding to said wheel wear of said grinding wheel.

5. In a grinding machine,

(a) an increment type feeding mechanism having (b) means for advancing and retracting a grinding wheel relative to a workpiece for a grinding operation,

(c) the means for retracting said grinding wheel being operable to effect a retracting movement equal to or less than the amount of advance of said grinding wheel for a grinding operation,

(d) whereby each grinding operation begins with the operative surface of said grinding wheel at the same distance from the center of rotation of the Work,

(e) means to dress said grinding wheel comprising (f) a dressing tool,

(g) a feeding mechanism for said dressing tool,

(h) and means operable by said increment type feeding mechanism after a predetermined number of grinding operations to actuate said feeding mechanism for said dressing tool toadvance said dressing tool by an amount corresponding to the wear of said grinding wheel.

6. In a grinding machine,

(a) an increment type feeding mechanism having (b) means for advancing and retracting a grinding wheel relative to a workpiece for a grinding operation,

(c) the means for retracting said grinding wheel being operable to effect a retracting movement equal to or less than the amount of advance of said grinding wheel for a grinding operation,

(d) whereby each grinding operation begins with the operative surface of said grinding wheel at the same distance from the center of rotation of the work,

(e) means to dress said grinding wheel comprising (f) a dressing tool,

(g) a feeding mechanism for said dressing tool,

(h) means operable by said increment type feeding mechanism after a predetermined number of grinding operations to actuate said feeding mechanism for said dressing tool to advance said dressing tool by an amount corresponding to the wear of said grinding wheel,

(i) comprising an actuating member,

(j) connections between said actuating member and said feeding mechanism so that said actuating member is moved in response to the advance of said increment type feeding mechanism, whereby said actuating member advances progressively,

(k) said actuating member having angularly spaced actuating portions,

(1) and control means for said dressing tool feeding mechanism adapted to be actuated by one of said angularly spaced actuating portions after a predetermined number of grinding operations.

References Cited by the Examiner UNITED STATES PATENTS 2,895,265 7/1959 Hill 51-165 3,183,631 5/1965 Price et a1. 51-165 3,222,823 12/1965 Seidel 51165 LESTER M. SWINGLE, Primary Examiner. 

1. IN A GRINDING MACHINE, (A) A GRINDING WHEEL SUPPORT, (B) A GRINDING WHEEL ROTATABLY MOUNTED ON SAID WHEEL SUPPORT, (C) MEANS FOR EFFECTING RELATIVE FEEDING AND RETRACTING MOVEMENTS OF SAID WHEEL SUPPORT INCLUDING (D) A REVERSIBLE INCREMENT FEEDING MEANS FOR SAID GRINDING WHEEL, (E) SAID INCREMENT FEEDING MEANS SERVING TO ADVANCE SAID WHEEL SUPPORT PROGRESSIVELY FARTHER FOR EACH GRINDING OPERATION BECAUSE OF WHEEL WEAR, (F) SAID INCREMENT FEEDING MEANS BEING OPERABLE BY A FIXED AMOUNT FOR RETRACTING SAID WHEEL SUPPORT, (G) A DRESSING TOOL PERIODICALLY AND PROGRESSIVELY SEPARATED FROM SAID GRINDING WHEEL BECAUSE OF SAID WHEEL WEAR, (H) A SECOND INCREMENT FEEDING MECHANISM FOR FEEDING SAID DRESSING TOOL TOWARD THE OPERATIVE FACE OF SAID GRINDING WHEEL, (I) AND MEANS MOVABLE WITH SAID FIRST INCREMENT FEEDING MEANS AND OPERABLE AFTER A PREDETERMINED NUMBER OF GRINDING CYCLES TO ACTUATE SAID SECOND INCREMENT FEEDING MECHANISM TO ADVANCE SAID DRESSING TOOL TO OPERATIVE RELATION WITH SAID GRINDING WHEEL. 